Hi,

I have several optocouplers soldered to a perfboard in order to detect voltage in multiple AC lines. The output of each is connected to an input pin in an Arduino with the pullup resistor enabled in software. The input AC voltage is 17VAC. Each optocoupler's input resistor is 1.2Kohm. So, one line of the AC runs through the input resistor to pin 1 on the chip. Pin 2 goes through a switch to the other AC line. Pin 5 is connected to the input pin on the Arduino and pin 6 to ground on the Arduino.

Most of them work fine, but a couple do not and I cannot figure out why. I've swapped out chips and tested connectivity wherever I can. I verified there is a 17 VAC drop across the input resistor and I've measure 1.2Kohm on the resistor.

Any suggestions to try to diagnose the issue? If it's something stupid I'm missing it.

Thanks.

 

Hi,

I have several optocouplers soldered to a perfboard in order to detect voltage in multiple AC lines. The output of each is connected to an input pin in an Arduino with the pullup resistor enabled in software. The input AC voltage is 17VAC. Each optocoupler's input resistor is 1.2Kohm. So, one line of the AC runs through the input resistor to pin 1 on the chip. Pin 2 goes through a switch to the other AC line. Pin 5 is connected to the input pin on the Arduino and pin 6 to ground on the Arduino.

Most of them work fine, but a couple do not and I cannot figure out why. I've swapped out chips and tested connectivity wherever I can. I verified there is a 17 VAC drop across the input resistor and I've measure 1.2Kohm on the resistor.

Any suggestions to try to diagnose the issue? If it's something stupid I'm missing it.

Thanks.

Remove the ground from the base. Otherwise, ground the base thru a high value resistor.

eT

 

Leave pin 6 unconnected and connect pin 4 to ground instead. This will make the coupling much more sensitive.